|Environmental Handbook Volume II: Agriculture, Mining/Energy, Trade/Industry (GTZ/BMZ, 1995, 736 pages)|
|Mining and energy|
|36. Surface mining|
Surface mining is the term used to describe diverse forms of raw-material extraction from near-surface deposits. It involves the complete removal of nonbearing surface strata (overburden) in order to gain access to the resource. Depending on the physical characteristics of the raw material and on the site-specific situation, various surface-mining techniques are applied:
Dry extraction of loose or solid raw materials: In hardrock mining, the product must first be "worked" (loosened). Then, it can be loaded, hauled and processed by mechanical means similar to those employed in loose-rock mining. Accordingly, dry surface mines require appropriate dewatering.
In wet-extraction, or dredging, operations, loose raw materials are mechanically or hydraulically extracted and transferred to a processing facility. The entire extraction equipment is normally located on/in the water, often floating on a river or artificial lake.
Offshore, or shelf, mining is the term used to describe the extraction of loose material from nearshore deposits (marine beach placers). Like in wet extraction, the material is excavated and conveyed by mechanical or hydraulic means.
Deep sea mining is a - future - form of mining in which raw materials are extracted from ocean beds; not to be dealt with in the present context.
The various surface mining techniques are applied to different types of raw material reservoirs.
Table 1 - Forms of surface mining and major raw-material products
|Hardrock mining||Loose-rock mining|
|dry extraction||dry extraction||wet extraction|
|building stones |
raw materials for cement
|metalliferous ores (copper, iron, silver, tin) |
|brown coal |
|heavy minerals (ilmenite, rutile,
RE-minerals1), zircon) |
heavy minerals (ilmenite, rutile, zircon, monazite)
1) RE-minerals = rare-earth minerals
Surface mines vary in size according to the nature of the deposit and the employed techniques of extraction. Among terrestrial workings, one encounters mines ranging in size from small one-man operations to huge strip mines measuring several kilometers in diameter. Due to the elaborate, expensive technology required, marine workings always strive toward minimum dimensions.
Since mining amounts to a site-bound activity, new and expanding operations often have to compete with other potential users of the premises in question, and the infrastructure required for surface mining operations may still have to be established. As regards the demarcation of surface mining activities, it is inherently difficult to separate them from the required mineral dressing facilities, because such processing normally takes place directly at the place of extraction.